CN109358690B - Transconductance constant control circuit and rail-to-rail operational amplifier - Google Patents
Transconductance constant control circuit and rail-to-rail operational amplifier Download PDFInfo
- Publication number
- CN109358690B CN109358690B CN201811174192.2A CN201811174192A CN109358690B CN 109358690 B CN109358690 B CN 109358690B CN 201811174192 A CN201811174192 A CN 201811174192A CN 109358690 B CN109358690 B CN 109358690B
- Authority
- CN
- China
- Prior art keywords
- input
- switch
- control
- electrically connected
- input unit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Automation & Control Theory (AREA)
- Amplifiers (AREA)
Abstract
The embodiment of the invention provides a transconductance constant control circuit and a rail-to-rail operational amplifier, and relates to the technical field of integrated circuits. The transconductance constant control circuit comprises a first switch, a second switch and a control unit, wherein the control unit is electrically connected with the first switch and the second switch, one end of the first switch is electrically connected between a bias circuit and a first input unit, the other end of the first switch is grounded, one end of the second switch is electrically connected between the bias circuit and a second input unit, the other end of the second switch is electrically connected with a power supply, the input end of the control unit is electrically connected with the input end of the first input unit and the input end of the second input unit, and the control unit is used for controlling one of the first switch and the second switch to be opened or closed according to an input signal so as to enable one of the first input unit and the second input unit to normally work, thereby realizing the constant transconductance of the rail-to-rail operational amplifier.
Description
Technical Field
The invention relates to the technical field of integrated circuits, in particular to a transconductance constant control circuit and a rail-to-rail operational amplifier.
Background
Transconductance refers to the ratio of the output current to the input voltage of a circuit cell. When an operational amplifier is used as a buffer, a common mode input range as large as the input signal range is required, and a rail-to-rail operational amplifier is required to obtain a large dynamic range. As shown in fig. 1, the common mode input (Vcm) of the rail-to-rail operational amplifier can be from the ground level (gnda) to the power supply voltage (vdda), and when the common mode input of the rail-to-rail operational amplifier changes from the ground level to the power supply voltage, the transconductance of the rail-to-rail operational amplifier changes in a very large range and cannot be kept constant, which makes frequency compensation difficult, and the gain and unit gain bandwidth change greatly, so that the performance of the circuit in a high frequency band is severely unstable.
Disclosure of Invention
The embodiment of the invention aims to provide a transconductance constant control circuit and a rail-to-rail operational amplifier so as to realize constant transconductance of the rail-to-rail operational amplifier.
In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:
in a first aspect, an embodiment of the present invention provides a transconductance constant control circuit, which is applied to a rail-to-rail operational amplifier, where the rail-to-rail operational amplifier includes a bias circuit, a first input unit, and a second input unit, the bias circuit is electrically connected to both the first input unit and the second input unit, transconductances of the first input unit and the second input unit during normal operation are equal, an input end of the first input unit is electrically connected to an input end of the second input unit, and the input ends of the first input unit and the second input unit are both used for receiving an input signal; the transconductance constant control circuit comprises a first switch, a second switch and a control unit, wherein the control unit is electrically connected with the first switch and the second switch, one end of the first switch is electrically connected between the bias circuit and the first input unit, the other end of the first switch is grounded, one end of the second switch is electrically connected between the bias circuit and the second input unit, the other end of the second switch is electrically connected with a power supply, and the input end of the control unit is electrically connected with the input end of the first input unit and the input end of the second input unit; the control unit is used for controlling one of the first switch and the second switch to be opened or closed according to the input signal so as to enable one of the first input unit and the second input unit to work normally, and therefore constancy of transconductance of the rail-to-rail operational amplifier is achieved.
In a second aspect, an embodiment of the present invention further provides a rail-to-rail operational amplifier, which includes a bias circuit, a first input unit, a second input unit, and the transconductance constant control circuit of the first aspect.
Compared with the prior art, the embodiment of the invention has the following beneficial effects:
the transconductance constant control circuit and the rail-to-rail operational amplifier provided by the embodiment of the invention comprise a bias circuit, a first input unit and a second input unit, wherein the bias circuit is electrically connected with the first input unit and the second input unit, the transconductance of the first input unit and the transconductance of the second input unit are equal when the first input unit and the second input unit work normally, the input end of the first input unit is electrically connected with the input end of the second input unit, the input end of the first input unit and the input end of the second input unit are used for receiving an input signal, the transconductance constant control circuit comprises a first switch, a second switch and a control unit, the control unit is electrically connected with the first switch and the second switch, one end of the first switch is electrically connected between the bias circuit and the first input unit, the other end of the first switch is grounded, one end of the second switch is electrically connected between the bias circuit and the second input unit, the other end of the second switch is electrically connected with a power supply, and the input end of the control unit is electrically connected with the input end of the first input unit and the input end of the second input unit; the control unit is used for controlling one of the first switch and the second switch to be opened or closed according to the input signal so as to enable one of the first input unit and the second input unit to work normally, and therefore constancy of transconductance of the rail-to-rail operational amplifier is achieved. That is, when the control unit controls the first switch to be turned on and the second switch to be turned off, the first input unit in the rail-to-rail operational amplifier does not work and the second input unit works normally, and when the control unit controls the first switch to be turned off and the second switch to be turned on, the first input unit in the rail-to-rail operational amplifier works normally and the second input unit does not work, so that the first input unit and the second input unit are prevented from working simultaneously, and transconductance of the rail-to-rail operational amplifier is transconductance when the first input unit works normally or transconductance when the second input unit works normally.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 shows a common-mode input schematic of a prior art rail-to-rail operational amplifier.
Fig. 2 is a graph illustrating the transconductance of a rail-to-rail operational amplifier as a function of input voltage in the prior art.
Fig. 3 shows a block diagram of a rail-to-rail operational amplifier provided by an embodiment of the present invention.
Fig. 4 is a schematic circuit diagram of a rail-to-rail operational amplifier according to an embodiment of the present invention.
Fig. 5 is a schematic diagram illustrating a circuit structure of a transconductance constant control circuit according to an embodiment of the present invention.
Fig. 6 shows a schematic diagram illustrating another circuit structure of the transconductance constant control circuit provided by the embodiment of the invention.
Fig. 7 is a schematic diagram illustrating another circuit structure of the transconductance constant control circuit provided in the embodiment of the present invention.
Fig. 8 shows a schematic diagram illustrating a circuit structure of a control unit provided by an embodiment of the present invention.
Fig. 9 is a schematic diagram illustrating another circuit structure of the control unit according to the embodiment of the present invention.
Fig. 10 shows a graph illustrating the transconductance of the rail-to-rail operational amplifier provided by the embodiment of the invention as a function of the input voltage.
Icon: 10-rail-to-rail operational amplifier; 100-transconductance constant control circuit; 200-a bias circuit; 300-a first input unit; 400-a second input unit; 500-a power supply; 110-a first switch; 120-a second switch; 130-a control unit; 310-first input pair tube; 410-second input pair tube.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present invention, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.
In the process of implementing the technical scheme of the embodiment of the invention, the inventor of the application finds that:
the reason that the transconductance of the rail-to-rail operational amplifier is not constant is that when the PMOS input pair transistor and the NMOS input pair transistor operate simultaneously, the transconductance is larger than that when only one input pair transistor operates, as shown in fig. 2, when the input voltage (vinn) of the rail-to-rail operational amplifier is close to the power supply voltage (i.e., vinn > Vdsat + Vgsp), the PMOS input pair transistor of the rail-to-rail operational amplifier will enter a linear region to operate, and at this time, the transconductance of the PMOS input pair transistor will decrease, and when the input voltage is further close to the power supply voltage, the PMOS input pair transistor will be completely cut off, and at this time, the transconductance of the PMOS input pair transistor is 0; similarly, when the input voltage is close to ground (i.e. vinn < Vdsat + Vgsn), the NMOS input pair transistor will enter linear operation, and the transconductance of the NMOS input pair transistor will decrease, and when the input voltage is further close to ground, the NMOS input pair transistor will be completely cut off, and the transconductance of the NMOS input pair transistor will be 0.
Based on the research on the defects, the embodiment of the invention provides a scheme for realizing the constancy of the transconductance of the rail-to-rail operational amplifier. It should be noted that the defects of the solutions in the above prior art are the results obtained after the inventor has made practice and careful study, therefore, the discovery process of the above problems and the solutions proposed by the following embodiments of the present invention to the above problems should be the contribution of the inventor to the present invention in the course of the present invention. The scheme for realizing the transconductance constancy of the rail-to-rail operational amplifier provided by the embodiment of the invention is explained in detail below.
Fig. 3 is a block diagram of a rail-to-rail operational amplifier 10 according to an embodiment of the present invention. The rail-to-rail operational amplifier 10 includes a transconductance constant control circuit 100, a bias circuit 200, a first input unit 300 and a second input unit 400, wherein the bias circuit 200 is electrically connected to both the first input unit 300 and the second input unit 400, transconductances of the first input unit 300 and the second input unit 400 during normal operation are equal, an input end vin1 of the first input unit 300 is electrically connected to an input end vin2 of the second input unit 400, and input ends vin1 of the first input unit 300 and an input end vin2 of the second input unit 400 are both configured to receive an input signal. The input end vin1 of the first input unit 300 and the input end vin2 of the second input unit 400 are used together as an input end of the rail-to-rail operational amplifier 10 to receive the input signal, the bias circuit 200 is configured to provide a first bias voltage Vbssn and a second bias voltage Vbssp to the first input unit 300 and the second input unit 400, respectively, the first input unit 300 operates normally according to the first bias voltage Vbssn, and the second input unit 400 operates normally according to the second bias voltage Vbssp.
The transconductance constant control circuit 100 includes a first switch 110, a second switch 120 and a control unit 130, the control unit 130 is electrically connected to the first switch 110 and the second switch 120, one end of the first switch 110 is electrically connected between the bias circuit 200 and the first input unit 300, the other end of the first switch 110 is grounded, one end of the second switch 120 is electrically connected between the bias circuit 200 and the second input unit 400, the other end of the second switch 120 is electrically connected to a power supply 500, an input end vin3 of the control unit 130 is electrically connected to an input end vin1 of the first input unit 300 and an input end of the second input unit 400, that is, the input end vin3 of the control unit 130, the input end vin1 of the first input unit 300 and the input end of the second input unit 400 receive the same input signal.
The control unit 130 is configured to control one of the first switch 110 and the second switch 120 to open or close according to the input signal, so that one of the first input unit 300 and the second input unit 400 operates normally, thereby achieving a constant transconductance of the rail-to-rail operational amplifier 10. Since the transconductances of the first input unit 300 and the second input unit 400 are equal when the first input unit 300 and the second input unit 400 normally operate, when only one input unit (i.e., the first input unit 300 or the second input unit 400) of the rail-to-rail operational amplifier 10 always operates normally, the transconductances of the rail-to-rail operational amplifier 10 can only be the transconductances of the first input unit 300 when it operates normally or the transconductances of the second input unit 400 when it operates normally, thereby achieving the constant transconductances of the rail-to-rail operational amplifier 10. In this embodiment, the input signal may be a signal in the form of a voltage, such as the input voltage vinn shown in fig. 3; in other embodiments, the input signal may be other forms of signals (e.g., a current signal), and the other forms of input signals may be converted into a voltage signal by the voltage conversion device.
In this embodiment, the rail-to-rail operational amplifier 10 may adopt the circuit structure shown in fig. 4, the first input cell 300 includes a first input pair of transistors 310 and a first tail current source Mssn, the first tail current source Mssn adopts an NMOS transistor, a gate of the first tail current source Mssn is electrically connected to the bias circuit 200 and one end of the first switch 110, a source of the first tail current source Mssn is grounded, a drain of the first tail current source Mssn is electrically connected to the first input pair transistor 310, the second input cell 400 includes a second input pair transistor 410 and a second tail current source mspp, the second tail current source mspp adopts a PMOS transistor, a gate of the second tail current source mspp is electrically connected to the bias circuit 200 and one end of the second switch 120, a source of the second tail current source mspp is electrically connected to the power supply 500, and a drain of the second tail current source mspp is electrically connected to the second input pair transistor 410. The first input pair transistors 310 all adopt NMOS transistors, the second input pair transistors 410 all adopt PMOS transistors, and the transconductance of the first input pair transistors 310 in normal operation is equal to the transconductance of the second input pair transistors 410 in normal operation. Specifically, the first input pair transistor 310 includes a first NMOS transistor MN1 and a second NMOS transistor MN2, the second input pair transistor 410 includes a first PMOS transistor MP1 and a second PMOS transistor MP2, a gate of the second NMOS transistor MN2 serves as the input terminal vin1 of the first input unit 300, and a gate of the second PMOS transistor MP2 serves as the input terminal vin2 of the second input unit 400. In this embodiment, the first bias voltage Vbssn is preferably high to turn on the first tail current source Mssn, and the first input pair transistor 310 normally operates, and the second bias voltage Vbssp is preferably low to turn on the second tail current source Mssp, and the second input pair transistor 410 normally operates. When the control unit 130 controls the on/off of the first switch 110 and the second switch 120 according to the input voltage vinn of the rail-to-rail operational amplifier 10, it needs to ensure that one of the first switch 110 and the second switch 120 is in a closed state and the other is in an open state, so that when the first switch 110 is open and the second switch 120 is closed, the first tail current source Mssn is turned on, the first input pair transistor 310 normally operates, the second tail current source Mssp is turned off due to the high gate voltage, and the second input pair transistor 410 cannot normally operate; when the first switch 110 is closed and the second switch 120 is opened, the first tail current source Mssn is opened due to the gate voltage being pulled low, the first input pair transistor 310 cannot normally operate, the second tail current source Mssp is turned on, and the second input pair transistor 410 normally operates. Therefore, the first input pair transistor 310 and the second input pair transistor 410 can be prevented from working simultaneously, so that the transconductance of the rail-to-rail operational amplifier 10 is always equal to the transconductance of the first input pair transistor 310 in working or the transconductance of the second input pair transistor 410 in working, and the transconductance of the first input unit 300 in working is equal to the transconductance of the second input unit 400 in working, so that the transconductance of the rail-to-rail operational amplifier 10 is constant.
In this embodiment, the first switch 110 and the second switch 120 may be implemented by MOS transistors, the control unit 130 may be implemented by a schmitt trigger, and the input signal is an input voltage vinn. As shown in fig. 5, the first switch 110 may be an NMOS transistor, the second switch 120 may be a PMOS transistor, the gate of the first switch 110 is electrically connected to the control unit 130, the source of the first switch 110 is grounded, the drain of the first switch 110 is electrically connected between the bias circuit 200 and the first input unit 300, the gate of the second switch 120 is electrically connected to the control unit 130, the source of the second switch 120 is electrically connected to the power supply 500, and the drain of the second switch 120 is electrically connected between the bias circuit 200 and the second input unit 400.
An input terminal vin4 of the schmitt trigger is electrically connected to both the input terminal vin1 of the first input unit 300 and the input terminal vin2 of the second input unit 400, and an output terminal of the schmitt trigger is electrically connected to both the gate of the first switch 110 and the gate of the second switch 120. The schmitt trigger is configured to output a control signal ctl to the gates of the first switch 110 and the second switch 120 according to the input voltage vinn and a preset flipping threshold Vth _ smt, so as to control one of the first switch 110 and the second switch 120 to be opened or closed by the control signal ctl.
In this embodiment, the input vin4 of the schmitt trigger is the input vin3 of the control unit 130, and is used for receiving the input voltage vinn; the predetermined threshold Vth _ smt should satisfy Vdast + Vgsn < Vth _ smt < Vdast + Vgsp, and is preferably 0.5 vdda. When the input voltage vinn of the schmitt trigger is smaller than the preset turning threshold Vth _ smt, the control signal ctl output to the gate of the first switch 110 and the gate of the second switch 120 is at a high level, at this time, the first switch 110 is turned on, and the second switch 120 is turned off; when the input voltage vinn is greater than the preset inversion threshold Vth _ smt, the control signal ctl output to the gate of the first switch 110 and the gate of the second switch 120 is at a low level, and at this time, the first switch 110 is turned off and the second switch 120 is turned on.
In this embodiment, the first switch 110 and the second switch 120 may be implemented by MOS transistors, the control unit 130 may be implemented by a comparator, and the input signal is an input voltage vinn. As shown in fig. 6, the first input terminal vin5 of the comparator is electrically connected to the input terminals vin1 of the first input unit 300 and vin2 of the second input unit 400, the second input terminal vin6 of the comparator is used for receiving a reference voltage vref, and the output terminal of the comparator is electrically connected to the gates of the first switch 110 and the second switch 120. The comparator is configured to output a control signal ctl to the gate of the first switch 110 and the gate of the second switch 120 according to the input voltage vinn and the reference voltage vref, so as to control one of the first switch 110 and the second switch 120 to be opened or closed through the control signal ctl.
In this embodiment, the first input vin5 of the comparator is the input vin3 of the control unit 130, and is used for receiving the input voltage vinn; the reference voltage vref should satisfy Vdrain + Vgsn < vref < Vdrain + Vgsp, preferably 0.5 vdda. When the input voltage vinn is less than the reference voltage vref, the comparator outputs a control signal ctl to the gate of the first switch 110 and the gate of the second switch 120 at a high level, at this time, the first switch 110 is turned on, and the second switch 120 is turned off; when the input voltage vinn is greater than the reference voltage vref, the control signal ctl output to the gate of the first switch 110 and the gate of the second switch 120 is at a low level, and at this time, the first switch 110 is turned off and the second switch 120 is turned on.
In the present embodiment, the comparator is preferably a hysteresis comparator to avoid switching the first pair of input transistors 310 in the first input unit 300 and the second pair of input transistors 410 in the second input unit 400 back and forth when the input voltage vinn of the rail-to-rail operational amplifier 10 is near the reference voltage vref.
In this embodiment, the first switch 110 and the second switch 120 may also be implemented by transmission gates. As shown in fig. 7, the control unit 130 includes a first output terminal vo1 and a second output terminal vo2, the first switch 110 includes a first connection terminal a1, a second connection terminal a2, a first control terminal C1 and a second control terminal C2, the first connection terminal a1 is electrically connected between the bias circuit 200 and the first input unit 300, the second connection terminal a2 is grounded, the first control terminal C1 is electrically connected to the first output terminal ctl1, and the second control terminal C2 is electrically connected to the second output terminal vo 2; the second switch 120 includes a third connection terminal A3, a fourth connection terminal a4, a third control terminal C3 and a fourth control terminal C4, the third connection terminal A3 is electrically connected to the power supply 500, the fourth connection terminal a4 is electrically connected between the bias circuit 200 and the second input unit 400, the third control terminal C3 is electrically connected to the second output terminal vo2, and the fourth control terminal C4 is electrically connected to the first output terminal vo 1.
As shown in fig. 8, in one embodiment, the control unit 130 includes a schmitt trigger and an inverter, an input vin4 of the schmitt trigger is electrically connected to both the input vin1 of the first input unit 300 and the input vin2 of the second input unit 400, an output of the schmitt trigger is electrically connected to an input of the inverter, an output of the schmitt trigger is the first output vo1, and an output of the inverter is the second output vo 2. The schmitt trigger is configured to output a first control signal ctl1 to the input terminal of the inverter, the first control terminal C1 and the fourth control terminal C4 according to the input voltage vinn and a preset flipping threshold Vth _ smt, and the inverter is configured to output a second control signal ctl2 to the second control terminal C2 and the third control terminal C3 according to the first control signal ctl1, so as to control one of the first switch 110 and the second switch 120 to be opened or closed by the first control signal ctl1 and the second control signal ctl 2. For example, when the input voltage vinn is less than the preset flipping threshold Vth _ smt, the schmitt trigger outputs the first control signal ctl1 to the input terminal of the inverter, the first control terminal C1 and the fourth control terminal C4 at a high level, and outputs the second control signal ctl2 to the second control terminal C2 and the third control terminal C3 at a low level, so that the first switch 110 is turned on and the second switch 120 is turned off; when the input voltage vinn is greater than the preset inversion threshold Vth _ smt, the first control signal ctl1 output to the input terminal of the inverter, the first control terminal C1, and the fourth control terminal C4 is at a low level, and the second control signal ctl2 output to the second control terminal C2 and the third control terminal C3 is at a high level, at this time, the first switch 110 is turned off, and the second switch 120 is turned on.
In another embodiment, as shown in fig. 9, the control unit 130 includes a comparator and an inverter, a first input terminal vin5 of the comparator is electrically connected to both the input terminal vin1 of the first input unit 300 and the input terminal vin2 of the second input unit 400, a second input terminal vin6 of the comparator is configured to receive a reference voltage vref, an output terminal of the comparator is electrically connected to an input terminal of the inverter, an output terminal of the comparator is the first output terminal vo1, and an output terminal of the inverter is the second output terminal vo 2. The comparator is configured to output a first control signal ctl1 to the input terminal of the inverter, the first control terminal C1, and the fourth control terminal C4 according to the input voltage vinn and the reference voltage vref, and the inverter is configured to output a second control signal ctl2 to the second control terminal C2 and the third control terminal C3 according to the first control signal ctl1, so as to control one of the first switch 110 and the second switch 120 to be opened or closed by the first control signal ctl1 and the second control signal ctl 2. For example, when the input voltage vinn is less than the reference voltage vref, the comparator outputs the first control signal ctl1 to the input terminal of the inverter, the first control terminal C1 and the fourth control terminal C4 at a high level, and the inverter outputs the second control signal ctl2 to the second control terminal C2 and the third control terminal C3 at a low level, so that the first switch 110 is turned on and the second switch 120 is turned off; when the input voltage vinn is greater than the reference voltage vref, the first control signal ctl1 outputted to the input terminal of the inverter, the first control terminal C1, and the fourth control terminal C4 is at a low level, and the second control signal ctl2 outputted to the second control terminal C2 and the third control terminal C3 by the inverter is at a high level, and at this time, the first switch 110 is turned off, and the second switch 120 is turned on.
It can be seen that in the present application, the control unit 130 controls the on/off of the first switch 110 and the second switch 120 by comparing the input voltage vinn of the rail-to-rail operational amplifier 10 with the reference voltage vref (or the preset flipping threshold Vth _ smt), so as to control the rail-to-rail operational amplifier 10 to always operate with only one input pair transistor (the first input pair transistor 310 or the second input pair transistor 410), and thus, it can be ensured that the transconductance of the rail-to-rail operational amplifier 10 is kept constant when the input voltage vinn changes, as shown in fig. 10.
To sum up, the transconductance constant control circuit and the rail-to-rail operational amplifier provided in the embodiments of the present invention include a bias circuit, a first input unit and a second input unit, the bias circuit is electrically connected to both the first input unit and the second input unit, transconductances of the first input unit and the second input unit during normal operation are equal, an input end of the first input unit is electrically connected to an input end of the second input unit, the input ends of the first input unit and the second input unit are both used for receiving an input signal, the transconductance constant control circuit includes a first switch, a second switch and a control unit, the control unit is electrically connected to both the first switch and the second switch, one end of the first switch is electrically connected between the bias circuit and the first input unit, the other end of the first switch is grounded, one end of the second switch is electrically connected between the bias circuit and the second input unit, the other end of the second switch is electrically connected with a power supply, and the input end of the control unit is electrically connected with the input end of the first input unit and the input end of the second input unit; the control unit is used for controlling one of the first switch and the second switch to be opened or closed according to the input signal so as to enable one of the first input unit and the second input unit to work normally, and therefore constancy of transconductance of the rail-to-rail operational amplifier is achieved. That is, when the control unit controls the first switch to be turned on and the second switch to be turned off, the first input unit in the rail-to-rail operational amplifier does not work and the second input unit works normally, and when the control unit controls the first switch to be turned off and the second switch to be turned on, the first input unit in the rail-to-rail operational amplifier works normally and the second input unit does not work, so that the first input unit and the second input unit are prevented from working simultaneously, transconductance of the rail-to-rail operational amplifier is transconductance when the first input unit works normally or transconductance when the second input unit works normally, and transconductance of the rail-to-rail operational amplifier is constant because transconductance of the first input unit and transconductance of the second input unit when the first input unit works normally is equal to transconductance of the second input unit when the first input unit works normally.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
Claims (10)
1. A transconductance constant control circuit is applied to a rail-to-rail operational amplifier and is characterized in that the rail-to-rail operational amplifier comprises a bias circuit, a first input unit and a second input unit, wherein the bias circuit is electrically connected with the first input unit and the second input unit, the input end of the first input unit is electrically connected with the input end of the second input unit, and the input ends of the first input unit and the second input unit are used for receiving an input signal; the bias circuit is used for respectively providing a first bias voltage and a second bias voltage for the first input unit and the second input unit so that the first input unit can normally work according to the first bias voltage and the second input unit can normally work according to the second bias voltage;
the transconductance constant control circuit comprises a first switch, a second switch and a control unit, wherein the control unit is electrically connected with the first switch and the second switch, one end of the first switch is electrically connected between the bias circuit and the first input unit, the other end of the first switch is grounded, one end of the second switch is electrically connected between the bias circuit and the second input unit, the other end of the second switch is electrically connected with a power supply, and the input end of the control unit is electrically connected with the input end of the first input unit and the input end of the second input unit; the first input unit comprises a first input pair transistor and a first tail current source, the grid electrode of the first tail current source is electrically connected with the bias circuit and one end of the first switch, the source electrode of the first tail current source is grounded, and the drain electrode of the first tail current source is electrically connected with the first input pair transistor; the second input unit comprises a second input pair transistor and a second tail current source, the grid electrode of the second tail current source is electrically connected with the bias circuit and one end of the second switch, the source electrode of the second tail current source is electrically connected with the power supply, and the drain electrode of the second tail current source is electrically connected with the second input pair transistor; the transconductance of the first input pair transistor in normal operation is equal to the transconductance of the second input pair transistor in normal operation;
the control unit is configured to control one of the first switch and the second switch to be turned off or on according to the input signal, so that one of the first input pair transistor and the second input pair transistor works normally, and the transconductance of the rail-to-rail operational amplifier is equal to the transconductance of the first input pair transistor when the first input pair transistor works normally or the transconductance of the second input pair transistor when the second input pair transistor works normally, thereby achieving a constant transconductance of the rail-to-rail operational amplifier.
2. The transconductance constant control circuit according to claim 1, wherein the first switch is an NMOS transistor, the second switch is a PMOS transistor, a gate of the first switch is electrically connected to the control unit, a source of the first switch is grounded, a drain of the first switch is electrically connected between the bias circuit and the first input unit, a gate of the second switch is electrically connected to the control unit, a source of the second switch is electrically connected to the power supply, and a drain of the second switch is electrically connected between the bias circuit and the second input unit.
3. The transconductance constant control circuit according to claim 2, wherein said input signal is an input voltage, said control unit comprises a schmitt trigger, an input terminal of said schmitt trigger is electrically connected to both of an input terminal of said first input unit and an input terminal of said second input unit, and an output terminal of said schmitt trigger is electrically connected to both of a gate of said first switch and a gate of said second switch;
the Schmitt trigger is used for outputting control signals to the grid electrode of the first switch and the grid electrode of the second switch according to the input voltage and a preset overturning threshold value so as to control one of the first switch and the second switch to be opened or closed through the control signals.
4. The transconductance constant control circuit according to claim 2, wherein said input signal is an input voltage, said control unit comprises a comparator, a first input terminal of said comparator is electrically connected to both an input terminal of said first input unit and an input terminal of said second input unit, a second input terminal of said comparator is configured to receive a reference voltage, and an output terminal of said comparator is electrically connected to both a gate of said first switch and a gate of said second switch;
the comparator is used for outputting control signals to the grid of the first switch and the grid of the second switch according to the input voltage and the reference voltage so as to control one of the first switch and the second switch to be opened or closed through the control signals.
5. The transconductance constant control circuit of claim 4, wherein said comparator is a hysteresis comparator.
6. The transconductance constant control circuit according to claim 1, wherein the first switch and the second switch both employ transmission gates, the control unit includes a first output end and a second output end, the first switch includes a first connection end, a second connection end, a first control end and a second control end, the first connection end is electrically connected between the bias circuit and the first input unit, the second connection end is grounded, the first control end is electrically connected with the first output end, and the second control end is electrically connected with the second output end;
the second switch comprises a third connecting end, a fourth connecting end, a third control end and a fourth control end, the third connecting end is electrically connected with the power supply, the fourth connecting end is electrically connected between the bias circuit and the second input unit, the third control end is electrically connected with the second output end, and the fourth control end is electrically connected with the first output end.
7. The transconductance constant control circuit according to claim 6, wherein said input signal is an input voltage, said control unit comprises a schmitt trigger and an inverter, an input terminal of said schmitt trigger is electrically connected to both of an input terminal of said first input unit and an input terminal of said second input unit, an output terminal of said schmitt trigger is electrically connected to an input terminal of said inverter, an output terminal of said schmitt trigger is said first output terminal, and an output terminal of said inverter is said second output terminal;
the schmitt trigger is configured to output a first control signal to the input end, the first control end, and the fourth control end of the inverter according to the input voltage and a preset flipping threshold, and the inverter is configured to output a second control signal to the second control end and the third control end according to the first control signal, so as to control one of the first switch and the second switch to be turned on or off according to the first control signal and the second control signal.
8. The transconductance constant control circuit according to claim 6, wherein said input signal is an input voltage, said control unit comprises a comparator and an inverter, a first input terminal of said comparator is electrically connected to both an input terminal of said first input unit and an input terminal of said second input unit, a second input terminal of said comparator is for receiving a reference voltage, an output terminal of said comparator is electrically connected to an input terminal of said inverter, an output terminal of said comparator is said first output terminal, and an output terminal of said inverter is said second output terminal;
the comparator is configured to output a first control signal to the input terminal, the first control terminal, and the fourth control terminal of the inverter according to the input voltage and the reference voltage, and the inverter is configured to output a second control signal to the second control terminal and the third control terminal according to the first control signal, so as to control one of the first switch and the second switch to be turned on or off by the first control signal and the second control signal.
9. The transconductance constant control circuit according to any one of claims 1 to 8, wherein said first tail current source is an NMOS transistor, and said second tail current source is a PMOS transistor.
10. A rail-to-rail operational amplifier comprising a bias circuit, a first input cell, a second input cell, and a transconductance constancy control circuit as claimed in any one of claims 1 to 8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811174192.2A CN109358690B (en) | 2018-10-09 | 2018-10-09 | Transconductance constant control circuit and rail-to-rail operational amplifier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811174192.2A CN109358690B (en) | 2018-10-09 | 2018-10-09 | Transconductance constant control circuit and rail-to-rail operational amplifier |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109358690A CN109358690A (en) | 2019-02-19 |
| CN109358690B true CN109358690B (en) | 2021-03-12 |
Family
ID=65348811
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811174192.2A Active CN109358690B (en) | 2018-10-09 | 2018-10-09 | Transconductance constant control circuit and rail-to-rail operational amplifier |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109358690B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110286259B (en) * | 2019-07-12 | 2021-10-08 | 浙江匠联科技有限公司 | Current peak value detection circuit |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1820411A (en) * | 2003-07-10 | 2006-08-16 | 皇家飞利浦电子股份有限公司 | Systematic offset free operational amplifier and apparatus comprising such an operational amplifier |
| CN101170299A (en) * | 2006-10-27 | 2008-04-30 | 恩益禧电子股份有限公司 | Operational amplifier and display device |
| CN102340284A (en) * | 2010-07-23 | 2012-02-01 | 复旦大学 | Low power voltage transconductance adjustable transconductance-constant rail-to-rail input operational amplifier |
| WO2012127956A1 (en) * | 2011-03-22 | 2012-09-27 | ルネサスエレクトロニクス株式会社 | Computation amplifier circuit, and display panel driver and display device employing same |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5278144B2 (en) * | 2009-04-28 | 2013-09-04 | セイコーエプソン株式会社 | Amplification circuit, integrated circuit device, and electronic apparatus |
-
2018
- 2018-10-09 CN CN201811174192.2A patent/CN109358690B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1820411A (en) * | 2003-07-10 | 2006-08-16 | 皇家飞利浦电子股份有限公司 | Systematic offset free operational amplifier and apparatus comprising such an operational amplifier |
| CN101170299A (en) * | 2006-10-27 | 2008-04-30 | 恩益禧电子股份有限公司 | Operational amplifier and display device |
| CN102340284A (en) * | 2010-07-23 | 2012-02-01 | 复旦大学 | Low power voltage transconductance adjustable transconductance-constant rail-to-rail input operational amplifier |
| WO2012127956A1 (en) * | 2011-03-22 | 2012-09-27 | ルネサスエレクトロニクス株式会社 | Computation amplifier circuit, and display panel driver and display device employing same |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109358690A (en) | 2019-02-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR100693821B1 (en) | Differential amplifier and active load for the same | |
| US8502603B2 (en) | Output common mode voltage stabilizer over large common mode input range in a high speed differential amplifier | |
| US11316483B2 (en) | Input voltage endurance protection architecture | |
| US9264031B2 (en) | Rail-to-rail input hysteresis comparator | |
| KR100877626B1 (en) | Class AB Amplifier and Input stage circuit for the same | |
| CN112821875B (en) | Amplifier circuit | |
| KR100462467B1 (en) | Variable gain amplifier circuitry in automatic gain control | |
| CN109358690B (en) | Transconductance constant control circuit and rail-to-rail operational amplifier | |
| US20190363679A1 (en) | Negative capacitance circuits including temperature-compensation biasings | |
| US20060049873A1 (en) | Rail-to-rail differential input amplification stage with main and surrogate differential pairs | |
| US10574200B2 (en) | Transconductance amplifier | |
| US8890612B2 (en) | Dynamically biased output structure | |
| Centurelli et al. | A new class-AB flipped voltage follower using a common-gate auxiliary amplifier | |
| CN114326895A (en) | Comparator circuit capable of expanding input range | |
| JP2010233084A (en) | Differential amplifier | |
| CN109120232A (en) | Suitable for low noise, the high bandwidth trans-impedance amplifier of wide dynamic range | |
| US10418952B1 (en) | Amplifier with hysteresis | |
| Centurelli et al. | A very low-voltage differential amplifier for opamp design | |
| US9246455B2 (en) | Three stage amplifier | |
| CN115421546A (en) | Voltage buffer | |
| US7633343B2 (en) | Fully differential amplifier | |
| JP2009060376A (en) | Amplifier circuit, sample holding circuit using the same, and analog-digital converter using the circuit | |
| CN108494377B (en) | Operational amplifier circuit | |
| KR100499856B1 (en) | Variable gain amplifier | |
| US10236851B2 (en) | Wide bandwidth variable gain amplifier and exponential function generator |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |